An office chair is provided having a back assembly which is configured to provide supplemental support to the back of a chair occupant in addition to the support provided by the primary support surface of the chair back. The chair back includes a lumbar support unit having a lumbar support pad wherein asymmetric support is provided to the left and right halves of the lumbar pad. As such, the asymmetric support loads are independently adjustable to more comfortably support a chair occupant. The chair back also includes a pelvic support pad which is disposed vertically adjacent to the lumbar support.